[WebAssembly] Fix fixEndsAtEndOfFunction for delegate

Background:
CFGStackify's [[ https://github.com/llvm/llvm-project/blob/398f25340000f26d648ebbc7eae9dc401ffc7d5f/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp#L1481-L1540 | fixEndsAtEndOfFunction ]] fixes block/loop/try's return
type when the end of function is unreachable and the function return
type is not void. So if a function returns i32 and `block`-`end` wraps the
whole function, i.e., the `block`'s `end` is the last instruction of the
function, the `block`'s return type should be i32 too:
```
block i32
  ...
end
end_function
```

If there are consecutive `end`s, this signature has to be propagate to
those blocks too, like:
```
block i32
  ...
  block i32
    ...
  end
end
end_function
```

This applies to `try`-`end` too:
```
try i32
  ...
catch
  ...
end
end_function
```

In case of `try`, we not only follow consecutive `end`s but also follow
`catch`, because for the type of the whole `try` to be i32, both `try`
and `catch` parts have to be i32:
```
try i32
  ...
  block i32
    ...
  end
catch
  ...
  block i32
    ...
  end
end
end_function
```

---

Previously we only handled consecutive `end`s or `end` before a `catch`.
But now we have `delegate`, which serves like `end` for
`try`-`delegate`. So we have to follow `delegate` too and mark its
corresponding `try` as i32 (the function's return type):
```
try i32
  ...
catch
  ...
  try i32    ;; Here
    ...
  delegate N
end
end_function
```

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D101036